O/2 Sensor location
 

We've bought a racepak data recording system for our stocker. The paperwork from racepak says we need to put the O/2 sensor in the header tube about 12" from the header flange. I was planning on putting a sensor in each collector. It seems to me that it would be hard to tune a engine just getting a reading on one cylinder on each side.Can anyone with experience with this enlighten me about this racepak system. I'm beginning to think that I spent a bunch of money on something that all it's going to show me is how little I really know about tuning a car. Thanks for any replies.

Re: O/2 Sensor location
 

With just one O2 sensor you would be far better to put it in the collector, but not too close to the end. Try to get it right at the south side of the point all four tubes meet in the collector. The further from the end of the collector the better. You don't want the fresh air giving you false lean readings.

The very best would be an O2 sensor in each tube at least 12 inches from the exhaust port/flame travel.

Re: O/2 Sensor location
 

I disagree..
I have a Racepak Sportsman recorder with O2 and the primary tube location is far easier to tune with than the collector location.
I did move to different cylinders when I first started tuning with it to check cyl to cyl fuel distribution, but once my fuel distribution was confirmed , I went back to just 1 cylinder.
With a few good recordings under your belt ,you will see A/F ratio changes quickly on the data graph and know what it will do to your cars performance.
Call Greg Kelly and ask him about it , he is a wealth of knowledge about these recorders.

Re: O/2 Sensor location
 

Bill I'm in about the same boat as you. I've used a FAST wideband which I don't recommend to anybody but that's besides the point. I had it located in the collector right after the four tubes merge. The reading where so erratic going down track you couldn't really get ahold of what was happening. Now again this was just a live reading and not a recorded run to review it after the fact. I've talked to a few NMRA Hot Street guys that use the racepak and they are all very happy with the accuracy of the readings and if I remember right with the RP there is a way to average the reading from start to finish through the run and I don't recall exactly where their sensors was located. I think Tom's got a good idea there. Put a bung in each tube and move it around to fine the cylinder thats the leanest and tune off of that more less.

Now I think my readings on mine would have probably been better if I had a true megaphone/merge collector instead of the big Hookers collector. I think it was mixing in fresh air and making the readings all over the place.

Re: O/2 Sensor location
 

If you see erratic readings with the sensor in the collector, you have something wrong. The only time I have seen erratic readings going down the track, there was an intermittent misfire in one ylinder. Misfire = lean spike. Mine (and MANY others) have all been in the collector (mine are 3 1/2" straight) about ten years now. Never an erratic reading. If not using all 8, I would never put one in a primary tube. It needs to be at least a foot from the end of the collector.

Re: O/2 Sensor location
 

Kris , you are correct .
you can smooth out the O2 graph so it makes sense on the time line of the run.
Having read and interperted data recordings made for repairs on street vehicles at the JEEP dealership I worked for made it easier for me to use the RacePak O2 graph, but you can get a lot of data with a very few runs, and lean to interpert it .

Re: O/2 Sensor location
 

It probably is better on a carburetor car to have the O2 in the collector if only one. Intake manifold can make fuel distribution uneven cylinder to cylinder. If in the collector you need to have an extension with the O2 as close to the convergence of the four primary as possible. One in each primary within 20 inches of the exhaust valve is best. In fuel injected cars because fuel distribution is pretty equal based on the location of injectors one in primary tube can work well. It does for me.

Understand that everyone has their own opinion /experience and different O2 locations work good or not so with varying assemblies. What is important is that what ever data reviewed is understood for what it really is.

O2 in the primary tube will see less fresh air than when installed in the collector. Am convinced with the cams we run O2 will see some fresh air no matter where located and more so in the collector.

In the collector AF will read more lean than if in primary tube. Check plugs and exhaust ports / headers. They don't lie. Be careful when helpful people say it should be this or that AF. My last motor was lifting the head trying to run it as lean as was being advised. They had O2 in collector while mine was in primary.

If you would like to get in the ballpark quickly spend a day on a chassis dyno with a good tuner. Review sheets from your the best runs. Those AF numbers are real for your assembly. Maintain and test variations on those.

In Div 1 there is a good tuner in Danbury CT.

Good Luck and Have Fun!

Re: O/2 Sensor location
 

Lot of good info here.

I recommend the bung in a primary tube AND a couple of bungs elsewhere. Like Tom says once you find a primary that "speaks for the whole engine" go with that.

I have had a lot of different O2's on my car (including 2 different brands in the same tube) and really like the Racepak. Having said that, any of these tools should be balanced with what the time slip says and your gut or a second source of info like plugs etc.

To get the average AF with Racepak data link:

1. activate the AF channel
2. select the AF channel in the file/grid box at the top of the graph area.
3. place the cursor on the start point and left click, then push the [ key on the keyboard
4. place the cursor on the end point of the time of interest and left click, then push the ] key on the key board

other help & tips: http://www.motorsportsinnovations.co...-help-tips.htm

http://www.motorsportsinnovations.co...verage-af1.jpg

Re: O/2 Sensor location
 

hi, we ran aO2 sensor in collector, reading was within .3 whole run. I also, look up in collector with a light, if its white, =lean, black =rich, dark grey,= about right .

Re: O/2 Sensor location
 

I have my O2 about 8 inches from the end of the collector. In order to get a proper reading at idle I have to put on a 24 inch extension made from flex pipe.
I can't reley on the O2 reading below 4,000 rpms without the extension on. After 4,000 or so it reads fine.
One thing I have noticed though is that the O2 reading is higher (leaner) in first and second gear, than in high at the same rpm's.
I've been tuning off of the high gear readings. And it seems to work.

Re: O/2 Sensor location
 

We locate ours right after or right before the minor diameter in the merge, preferably before, so it is as far from the end of the collector as possible. If not using a merge, 4-6" from the ends of the primaries. Also, between 10 and 2 o'clock, if possible, so as to prevent moisture from condensing in the sensor when it is off. The sensors aren't real happy lighting off with water in them. You may see some fluctuation at idle, or rolling along in the pits or staging lanes, due to fresh air being drawn back into the collector at low RPM, but when it really matters, going down the track, it will be fine.

Re: O/2 Sensor location
 

Mine shows excessively lean at low rpms. I once tried to tune the idle before I knew about the extension trick. And it was smoking black and still showing lean.

Re: O/2 Sensor location
 

That's it and it is just as bad on the 2 step. Shows real lean.
Over 4,000 rpms it seems to work fine.

Re: O/2 Sensor location
 

Problem with putting it in a primary tube is, if you get something in a jetborvinjector you won't see it in your run log. With it in the collectors, you will see a lean indication. You won't know which Cyl, but you will know which bank. If it develops a misfire for any reason you will see a lean indication, but a misfire from ignition, etc) you won't always hear it at high RPM) will cause an erratic reading. A misfire causes lean spikes. Only way I would want one in a primary would be having one in each tube.
I know I don't know everything, but have been tuning EFI cars for 23 years now, and have done it both ways. I much prefer them in the collectors, at least a foot from the end.

Re: O/2 Sensor location
 

I thank everyone for their reply's. This is one of the nice things about the forum ; your just a keystroke away from finding out just about anything. Since I have a small diameter and relatively long collector I'm going to put the sensor just past the point that it merges. I think it will probably work out ok there.

Re: O/2 Sensor location
 

I think that is your best option at this point. That being said, I am in the process of putting one in each tube and in the collector for a total of 9 on my car. Surely, I should be able to figure this tuning thing out somewhat.

Re: O/2 Sensor location
 

Hi Ed. Not to steal the thread. But can you tell me how I come out of the trailer. Warm the car up. Then make a run pops and bangs all the way down the track. Check A/F/R it looks fine everything in the data logger looks normal. Make zero changes go for another pass the car runs clean not a pop or bang Picks up 2 1/2 tenths. Datalogging looks the same as the first run?. Car runs clean the rest of the day.

Re: O/2 Sensor location
 

Art, is the coolant temp the same? Anytime I have had one pop & bang it has looked lean. If the engine is cooler I would guess it's a tad lean. My stuff always goes down the track quickest richer than the dyno liked. If your problem is at lower temps you might try adding a little fuel in your air/fuel coolant temp correction table, at the temp you are seeing first pass. That's providing you don't warm
It up to the same temp it runs at the rest of the day.

Re: O/2 Sensor location
 

Coolant was actually 1 degree (centigrade) hotter (67 to 66) on the first run, than the second. And equal in latter runs.
I was wondering if in starting and warmup I'm fouling the plugs. And it takes a run to clean them?
I've got to work on the start fuel map, it does not like to start cold. pops out the throttlebodies like mad.

Re: O/2 Sensor location
 

Art, I would warm it up, then pull the plugs. They should be pretty much white. If they are black, you found it. If you can slip a muffler on it, or an extension about two feet long, you can idle it & drive it up and down the return road to find where it is so rich. Try to make it run 14-1 to 14.7-1 air/fuel at idle and all part throttle areas of the map. You can get a look at the decelloration a/f if you leave the logger on as you slow down. I think your probably cleaning the plugs up on the first pass. I'm surprised at how many black spark plugs I see guys pull out after warming them up. I hear over- rich cars driving around the pits all the time. Maybe they are trying to tune that part with open collectors?

Re: O/2 Sensor location
 

Do you fog the engine after every race day? Next time you head to the track, do your warm up and pull the carb to check intake plenum, I bet some of the oil is present until you make a complete pass washes it out.

Ian

Re: O/2 Sensor location
 

No Carbs. I can look into the combustion chamber. Just by opening the throttle plates. Haven't fogged it. Leaks down 3% or better.
Going to try a new set of plugs old ones have about 75 runs on them. And I don't have a MSD to keep them clean.



http://i203.photobucket.com/albums/aa12/rt1092/003.jpg

Re: O/2 Sensor location
 

Where's the "Like" button?